1. Field of the Invention
The present invention relates to a plasma polishing apparatus and a plasma polishing method in a semiconductor process and, more particularly to, a dry polishing apparatus and a dry polishing method of polishing a target object by a plasma without using a polishing solution.
2. Description of the Related Art
In manufacturing processes for semiconductor devices and liquid crystal displays, the surfaces of target objects are polished to reduce irregularity on the surfaces of the target objects such as semiconductor wafers and LCD substrates. As representative polishing of this type, a so-called CMP (Chemical Mechanical Polishing) method is known in which the surface of a target object is mechanically polished using a chemical polishing solution, a pad, and so forth.
FIGS. 11 and 12 show an example of a conventional CMP apparatus. This CMP apparatus comprises a rotary table 104 having a polishing pad 102 arranged on its surface. A wafer holder 106 rotated by a motor 112 (FIG. 12) is arranged above the table 104. A nozzle 108 for supplying the slurry of a chemical polishing solution containing, e.g., silica as a main component is arranged above the surface of the polishing pad 102.
In polishing, a wafer W as a target object is held by the holder 106 and pressed against the pad 102 at a predetermined pressure. In this state, both the table 104 and the holder 106 are rotated, and a polishing solution i s supplied from the nozzle 108. In this manner, the surface of the wafer W is polished a friction among the chemical polishing solution, the pad 102 and the surface of the wafer W.
Since the above-described CMP apparatus, however, polishes the wafer in a wet atmosphere by using a chemical polishing solution, it requires a scattering prevention mechanism for a polishing solution and a recovery mechanism for a waste solution. In addition, this CMP apparatus must perform the post-process step of cleaning a wafer after it is polished.
Since the polishing pad is pressed against the surface of a wafer in the above-described CMP apparatus, a progress of polishing the wafer surface cannot be directly observed. It is therefore difficult to detect the end of polishing. Further, this CMP apparatus uses many control parameters such as the pressure, the rotational speeds of the rotary table and the wafer holder, the supply amount of a polishing solution, and the polishing time, so that a wealth of experiences and know-how are required to perform optimum polishing.